SAN FRANCISCO—A team of system administrators, web developers, and health care professionals reported this week that Craigslist, the free online network of classified advertisements, has contracted the anogenital disease commonly known as HPV.

Administrators can't say for certain how many strangers have used the online classifieds site.

The shocking diagnosis, made after an hour-long examination of Craigslist's main server, marks the first time an Internet site has ever contracted a sexually transmitted virus.

"No doubt about it, that's definitely HPV," said Dr. Howard Morrison, a general practitioner who was brought in Tuesday to administer a series of tests on the popular website. "Looks like it's already attacked the central mainframe and several LAN routers. Pretty severe strain of it, too. One of the worst I've ever seen."

"Knowing what I do about Craigslist, though, I can't say that I'm surprised," Morrison added while scanning through lines of infected HTML code. "It was only a matter of time before something like this happened."

While tests were unable to determine how Craigslist contracted human papillomavirus, the site's casual relationships with more than 40 million users nationwide is likely to blame. Internal records revealed that Craigslist routinely allowed complete strangers to sign up on its site, the vast majority of them sexually perverse, morally depraved, and lacking even rudimentary hygiene skills.

"We tried to ignore the signs, but every day more and more of those weird wart-looking things started showing up on our home page," said a Craigslist developer who wished to remain anonymous. "I honestly didn't think it was possible, but the cotton swabs confirmed it. Craigslist has HPV."

Dr. Morrison swabs the Craigslist mainframe and advises an 80 percent reduction in traffic to avoid gonorrhea.

Founder Craig Newmark said he suspected that the sexually transmitted disease was contracted from the "Casual Encounters" section of the website, a popular service used by people looking to engage in consequence-free intercourse. Newmark did not rule out other potential sources of infection, however, including the many thousands of listings for "female help around the house," amateur modeling work, and free used mattresses.

"It could've been anyone, really," said Newmark, who estimated that between 90 and 95 percent of the site's users are HPV carriers. "Especially that landlord who offers rent- reduced apartments for certain 'unspecified services,' or that guy pimpdadder84 from Chicago, who's always posting want ads for previously owned underwear."

"Considering the kind of stuff that goes on in here, I'm relieved HPV was all we caught," Newmark added.

Since the diagnosis, Craigslist administrators have suspended all traffic to the website and started regular treatment for the virus. System analysts have been instructed to apply anti-inflammatory cream to affected WAN hubs, file servers, and other problem areas, as well as wash Craigslist's main Ethernet connections in podofilox topical solution three times daily.

Doctors have also recommended the website contact any past partners or clients and ask that they too get checked out for HPV.

"How could we have been so stupid?" embarrassed Craigslist site officer Michael Sturges said. "I knew it wasn't exactly safe, and that we shouldn't be allowing just anyone from anywhere to join. But I wanted for the site to be, you know, popular."

Added Sturges, "I can't believe we let those creeps get into our CMS database."

Though worrisome for all involved, this week's HPV diagnosis has reportedly taught the online network a number of valuable lessons. System administrators claimed that if and when the website finally returns, it would do so with a number of new policies.

Future users will be required to disclose their real names when registering with Craigslist, in addition to providing a brief summary of their past sexual history, taking a standard blood test, agreeing to a month-long trial period during which both site and user can better get to know each other, and entering a valid e-mail address.

Approximately 300 new firewalls will also be installed.

"You can never be too careful in this day and age," Craigslist security and network technician Sheila Wilder said. "Just look at MySpace. That poor site's been knocked up three times in the last year alone."